Feasibility of Sludge Ozonation for Stabilization and Conditioning

A pilot-scale sludge treatment plant was built to investigate the feasibility of ozonation processes for waste activated sludge treatment. Ozonation of wastewater sludge resulted in mass reduction by mineralization as well as by supernatant and filtrate recycle. Another advantage of sludge ozonation is a significant improvement of settleability and dewaterability. Experimental results showed that mass reduction of 70% and volume reduction of 85% compared with the control sludge was achieved through the sludge ozonation at a dose of 0.5?gO₃/gDS. It is also interesting to note that the filterability deteriorates up to ozone dose of 0.2?gO₃/gDS and then improves considerably at a higher ozone dose. The filterability could be improved by chemical conditioning even at a low ozone dose. The economic feasibility by cost analysis reveals that ozonation processes can be more economical than other alternative processes for sludge treatment and disposal at small-sized wastewater treatment plants.     

Incidence of an Ozonation Stage on the Treatment of Cherry Stillage by Activated Sludge

This article presents a laboratory study of the ozonation of diluted cherry stillage, a high-strength wastewater. Influence of variables, kinetics, and the effects of an ozonation stage coupled with the biological treatment by activated sludge are addressed. Single activated sludge processing was shown effective to remove biological oxygen demand (BOD) and chemical oxygen demand (COD) but polyphenols were reduced to a lesser extent. On the other hand, direct wastewater ozonation did not reduce COD and total organic carbon (TOC) appreciably, and foaming problems were experienced when a high gas flow rate was applied. However, polyphenols and UV₂₅₄ absorbance decreased substantially by means of ozonation. To best achieve complete cherry stillage purification, two ways of coupling ozonation with activated sludge are proposed. Ozonation prior to activated sludge is advised for high-concentration wastewater to reduce polyphenol concentration, thus removing inhibiting effects. For wastewater with low polyphenol concentration the sequence activated sludge–ozonation–activated sludge is preferred to enhance the overall process performance in terms of oxidation efficiency and sludge settling.     

Effect of Ozonation on Activated Sludge Solubilization and Mineralization

New strategies for sludge stabilization and mineralization need to be developed since the use of sludge in agriculture is debatable and sludge incineration cannot be a systematic solution. Minimization of sludge production should be preferred. In this work, the effect of ozone on activated sludge solubilization and mineralization during batch experiments is assessed by establishing carbon and ozone mass balances. After extended ozonation of the sludge, more than 90% of the particulate carbon is modified. Depending on the experimental conditions, from 15 to 50% is found in a soluble form and from 35% to 95% was mineralized. The VSS/SS ratio decreases from 86% to less than 50% illustrating the sludge mineralization. The initial rate of ozone consumption by the sludge is very high (estimated value: 30 mgO₃/g VSS.min) and corresponds to high rates of carbon solubilization and mineralization. More than 50% of the carbon obtained after ozonation is found to be readily biodegradable using a short-term BOD procedure.     

Organohalogen Formation During Oxidative Sludge Bulking Control

Effluent quality implications of bulking control with chlorine, hydrogen peroxide and ozone in activated sludge treatment have been studied on laboratory scale. Batch chlorination of sludge samples led to the formation of trihalomethanes, mainly as chloroform, in hundreds of μg/L and even more non-specified organohalogens. Most organohalogens detected were formed from substances in the effluent and fewer out of the sludge solids. The presence of sludge lessened the concentration of extractable trihalomethanes in the effluent. Ozone or hydrogen peroxide addition did not lead to the formation of any organohalogens. Continuous chlorination in a laboratory scale activated sludge plant did not produce measurable quantities of any organohalogen compounds.     

A TYPICAL APPLICATION OF MAGNETIC FIELD INWASTEWATER TREATMENT WITH FLUIDIZED BED BIOFILM REACTOR

The effects of a magnetic field on wastewater treatment with a fluidized bed biofilm reactor was investigated. With glucose being the sole carbon source, the activated sludge obtained from a real wastewater treatment plant was used as a seed. Magnetically loaded polystyrene beads at the size of 500-595 μm were used as support materials for biofilm formation in a fluidized bed biofilm reactor. Magnetic field application allowed the operation of the column at high liquid flow rates, thus external diffusion limitations on the biofilm surface were lowered and the efficiency of biodegradation was increased. Denser, thinner, and more active biofilm was obtained with magnetic field application, especially in pulsed form. As expected, the system performance changed with operational parameters, and the increase in substrate removal reached up to 26% with pulsed application of a 17.8 mT DC-magnetic field under optimum conditions.     

A typical application of magnetic field inwastewater treatment with fluidized bed biofilm reactor

The effects of a magnetic field on wastewater treatment with a fluidized bed biofilm reactor was investigated. With glucose being the sole carbon source, the activated sludge obtained from a real wastewater treatment plant was used as a seed. Magnetically loaded polystyrene beads at the size of 500-595 w m were used as support materials for biofilm formation in a fluidized bed biofilm reactor. Magnetic field application allowed the operation of the column at high liquid flow rates, thus external diffusion limitations on the biofilm surface were lowered and the efficiency of biodegradation was increased. Denser, thinner, and more active biofilm was obtained with magnetic field application, especially in pulsed form. As expected, the system performance changed with operational parameters, and the increase in substrate removal reached up to 26% with pulsed application of a 17.8 mT DC-magnetic field under optimum conditions.     

Sludge Ozonation and its Application to a New Advanced Wastewater Treatment Process with Sludge Disintegration

The applicability of sludge ozonation on wastewater treatment processes was investigated to reduce the amount of excess sludge without losing phosphorus removal efficiency. Solubilization degree per ozone consumption for general sludge was in the range from 2.4 to 5.8 gSS/O₃ and from 4.1 to 7.7 gCOD/gO₃. Around 80 to 90% of solubilized organics was biodegradable at a solubilization degree of 0.3. Based on the experimental results, a lab-scale plant with sludge ozonation and phosphorus crystallization was constructed to investigate the treatment performance. Amount of excess sludge was reduced by 93% with almost complete removal of soluble BOD and phosphorus removal efficiency of more than 80%. The percentage of the effluent COD_Cr discharge increased from 10% to 14–17% after installing ozonation and crystallization because of the formation of non-biodegradable organic substances in ozonation process. Energy consumption of the innovative advanced process is comparable or can be even smaller than that of the conventional anaerobic/oxic (A/O) process in spite of the installation of ozonation and crystallization.     

Improving the Biodegradation of Organic Pollutants with Ozonation during Biological Wastewater Treatment

Pre-ozonation is often used to enhance the biodegradability of recalcitrant compounds prior to biological treatment of wastewater. A usual shortcoming of such an approach is wasting ozone on other compounds that are already biodegradable. This research followed a groundbreaking approach of degrading a recalcitrant substance with ozone during biological treatment. Two parallel bench-top activated sludge processes were fed a synthetic wastewater containing typical biodegradable substances and also methylene blue at 5 mg/L. Ozone was applied continuously and directly into one of the activated sludge units at 17 mg/L based on inflow rate. The methylene blue was removed by 95%?in the ozonated process compared with just 40%?removal in the non-ozonated control. The removal in the activated sludge without ozonation was demonstrated to be mainly due to biosorption. The ozone oxidation reaction by-products were analyzed using GC-MS on volatile substances collected in the headspace above ozonated samples of methylene blue and most found to be biodegradable. These by-products are expected to be degraded and assimilated in the same process unit together with the other biodegradables in the feed stream by the activated sludge process. The reaction rate with organic substances depleted the dissolved ozone at such a rate that the inactivation of the treatment bacteria (and protozoa) was minimal, mostly affecting the filamentous bacteria. A concern that ozone, as a powerful disinfectant, could inhibit or kill the beneficial bacteria in the activated sludge process was proven to be incorrect.     

Intermittent Ozone Application in Aerobic Sludge Digestion

Excess biological sludge, WAS, produced during activated sludge process is a growing problem for the utilities owing to the stringent regulations now imposed worldwide. One method of handling the excess sludge is to digest it, to reduce its amount and to stabilize it. Aerobic digestion is particularly suitable for nutrient treating plants as sludge should not be exposed to anaerobiosis since this will lead to release of accumulated phosphorus. A novel and patented ozone-assisted aerobic sludge digestion process (PCT/TR2010/000213) is shown to appreciably shorten the 15–30-day aerobic digestion period and the extent of solids destroyed. WAS samples were ozonated for different periods in Erlenmeyer flasks, once a day, on each of four consecutive days. Flasks were continuously aerated between ozone applications. The MLVSS, MLSS, COD and OUR parameters were measured routinely during the course of four days of digestion in order to optimize the process. As a result 22.6%, 40%, 75% and 84% MLVSS reductions were obtained at total ozone applications of 0.42, 0.64, 0.85 and 1.27 mg O₃ g^?1 MLSS, at the end of the fourth day. Hence, it became possible to save on contact time as well as achieving a bio-solids digestion far exceeding the standard aerobic process, which is 40–50% in 15–30 days, at the expense of a minimum of ozone dose. The developed process is deemed superior over side-stream ozonation where ozone is applied to the return activated sludge, RAS, line; in that it does not cause any reduction in active biomass amount maintained in the aeration tank. Conversely, reduction in active biomass concentration results in reduced treatment efficiency.     

Effect of Ozone on Viability of Activated Sludge Detected by Oxygen Uptake Rate (OUR) and Adenosine-5′-triphosphate (ATP) Measurement

The current study focused on treatment of phenolic wastewater using an integrated process – dosing of ozone directly to activated sludge. The main goal was to analyze the effect of ozonation on viability of activated sludge in different systems – activated sludge in distilled water and activated sludge in wastewater. Two viability detection methods, oxygen uptake (OUR) rate and adenosine-5'-triphosphate measurement (ATP), were compared. The linear correlation between ATP and OUR measurements in studied range was found to be good (r² = 0.90). In case of ozonation of activated sludge in wastewater, ozone doses up to 42 mgO₃·gMLVSS^?1 did not influence the viability of sludge. In addition, contrary to ozonation of sludge in distilled water, soluble COD was reduced by 15.6% (at ozone dose of 42 mgO₃·gMLVSS^?1).     

Enhancement of biomass speciation in Step Sludge Recirculation activated sludge system by the use of submerged membranes

In this work the performances of the Step Sludge Recirculation (SSR) activated sludge process were improved by using submerged membranes. The SSR system used in the experiments consisted of an anoxic stage for the denitrification and four aerobic stages for the nitrification, followed by a sedimentation stage in order to separate the purified water from the biomass.This conventional SSR system was compared with an improved one by substituting the secondary clarifier with a submerged membrane module. Two different types of flat sheet membrane were fitted into the membrane module and checked on performances.The main objective of the work was to optimize the process in order to obtain a maximum in the removal of ammoniacal nitrogen. For all the tested systems, the activated sludge presented high microfauna density, and the system with submerged membranes presented highest efficiency in nitrogen removal.The use of membranes instead of a sedimentation tank has the additional advantage to selectively separate different microorganisms (among bacteria and protozoa) from the biomass, thus enhancing the overall efficiency of the biological process, with an increase equal up to 43%.     

CAST工艺在大连凌水河污水处理厂的应用

介绍了大连凌水河污水处理厂CAST工艺设计参数和工艺特点,实际运行中进出水水质情况及运行效果。分析了CAST工艺的进水方式、曝气量、污泥浓度等运行参数对污水处理效果的影响。凌水河污水处理厂的运行结果表明,CAST工艺对城市污水有较好的处理效果,出水指标稳定达到了《城镇污水处理厂污染物排放标准》（GB18918-2002）一级B标准。     

Applications of ozone for industrial wastewater treatment — A review

This paper presents a detailed review of published applications of ozone for treating many types of industrial wastewaters. Applications of ozone technologies to control pollution in full‐scale industrial wastewater treatment plants in the areas of recycling marine aquaria, electroplating wastes, electronic chip manufacture, textiles, and petroleum refineries, are discussed. The rising acceptance of ozone as a replacement bleaching agent for paper pulp to eliminate the discharge of halogenated effluents from pulp bleaching plants also is traced. Newer applications for ozone in treating rubber additive wastewaters, landfill leachates, and detergents in municipal wastewaters are summarized briefly. The combination of ozone oxidation followed by biological treatment has been installed full‐scale at a large German industrial chemical complex. Ozone coupled with ultraviolet radiation and/or hydrogen peroxide (advanced oxidation) is being utilized to destroy organic contaminants in groundwaters at munitions manufacturing plants and at Superfund sites (hazardous wastes). Ozone followed by activated carbon adsorption removes color and organics cost‐effectively from North African phosphoric acid.     

Bulking Reduced With The Use Of Ozone - Study Of The Mechanism Of Action Versus Bacteria

Ozone application at low level seems to be a good treatment to control bulking. The best treatment can be 0.5 to 1 mg O₃/g TVM.h (total volatile matter hour); φ_R = 30 min. The injection of the ozone is into the recirculation sludge pipe. It is possible to improve the settling and obtain good reduction of the dissolved organic matter. The mechanisms of ozone's action on the sludge is approached by the determination of byproducts: amino acids, sugars, phosphorus compounds.     

Reduction of Excess Sludge Produced by Biological Treatment Processes: Effect of Ozonation on Biomass and on Sludge∗

The excess sludge produced during biological treatment of wastewater can be reduced by treating this sludge with ozone in a specific reactor and recycling it to the biological facility. This increases the biodegradability of the inert fractions of the sludge without deteriorating the activity of the microorganisms. Ozone reacts only within the film zone near the gas/liquid interface: it is assumed that the size of the microflocs of active microorganisms is greater than the effective thickness of the film, thus protecting them from ozone. This coupled treatment produces treated water having satisfactory characteristics and a residual excess sludge that has an extremely high settling capability.     

油田污泥焚烧处理技术分析

油田污泥的处理是目前国内外各大油田面临的一个棘手问题。本文分析了各种常见焚烧炉装置在焚烧油田污泥时的特点,认为流化床焚烧炉比较适合油田污泥的焚烧。同时,对焚烧处理过程中的污泥预处理系统也进行了分析。根据对油田污泥焚烧后形成的排烟和排渣特点的分析,认为只要采取恰当的措施,焚烧处理方法能比较容易地满足相关排放标准。     

Characteristics of phenol degradation by immobilized activated sludge

The effects of various factors involved in phenol degradation through an immobilized activated sludge with a photo-crosslinked resin were investigated. The immobilized activated sludge showed a higher relative activity of phenol degradation across a broader range of pH than free activated sludge. A higher rate of phenol degradation was observed when the bead size was smaller. The phenol degradation in the free activated sludge was inhibited at the 3000 mg/L of phenol, while that in the immobilized activated sludge was maintained at the same concentration for 28 h without any inhibition. The degradation rates of phenol were not directly proportional to the increasing amount of immobilized bead dosage, but the phenol degradation was completed in a shorter time than that for the free activated sludge. For the repeated reaction of immobilized activated sludge, the relative activity is increased up to eight times after seven repeated initial cycles. Continued treatment of immobilized activated sludge showed more than 95% of phenol removal efficiency under a loading rate of 5.59 kg-phenol/(m³ d), which is twice as large as the loading rate for the free activated sludge.     

污泥干化技术综述及方案选择

由于日益规模化污水处理厂的污泥产量大、含水率高,体积巨大,带来环境、经济、技术等方面难题,污泥干化减量是污泥有效处置的关键环节。详细介绍了污泥电干化、热水干化等干化技术原理、工艺流程、优缺点和适用条件,给出了厂矿企业在污泥干化方案选择的适用条件,以期为技术方案选择、新设备、新工艺开发提供参考。     

Flotation efficiency of activated sludge flocs using population balance model in dissolved air flotation

The activated sludge process is one of the most frequently used processes for biological wastewater treatment. Conventional gravity sedimentation (CGS), which is widely used as a secondary clarifier in activated sludge processes, has a routine problem due to floating tendency, called bulking, caused by filamentous microorganisms. Dissolved air flotation (DAF) has been applied as potential alternative to CGS as a secondary clarifier. A series of experiments were performed to measure physico-chemical characteristics and removal efficiency of activated sludge flocs. The removal efficiency of flocs corresponding in lag and exponential growth phases was lower, while that of flocs both in stationary and endogenous phases considerably increased. The rise velocity of floc/bubble agglomerates was calculated by using a population balance (PB) model explaining the distribution of floc/bubble agglomerates. The experimental results of flotation efficiency showed a similar tendency with the results predicted by PB model for the rise velocity and distribution of floc/bubble agglomerates. It was found from our study that the DAF process was very effective as a secondary clarifier in the activated sludge process.     

高浓度中药废水生产废水处理工程实例

某制药公司中药提取生产废水中有机物和氨氮浓度高,水质、水量变化大,特别是醇沉废水,COD浓度高达300000 mg/L。该工程采用混凝沉淀—UASB—缺氧—好氧—曝气生物滤池组合工艺处理废水,UASB采用脉冲布水,好氧采用可提升曝气系统。进水CODCr、BOD5、NH4+、SS的质量浓度分别为12000、4000、60、3000 mg/L,出水指标达到《GB21906-2008中药类制药工业水污染物排放标准》表二新建企业建企业水污染物排放的要求,CODCr、BOD5、NH4+、SS的去除率分别为99.2%、99.6%、86.7%、98.3%。